Omni-stereo imaging research may involve the capture and display of stereoscopic (stereo) three-dimensional imagery for substantially all of an environment (omni). Many techniques have been developed for capturing omni-directional monoscopic imagery of an environment using wide-angle lenses, mirrors, and various image mosaicing techniques. Similarly, many techniques have been developed for capturing stereoscopic imagery. There are even some techniques that combine the two technologies to capture stereoscopic omni-directional (omni-stereo) imagery.
The predominant existing method uses spherical imagery that has been stored in an equirectangular image format, where the horizontal coordinate corresponds to longitude, and the vertical coordinate corresponds to latitude, for various points on the surface of a sphere. The equirectangular image format is used for viewing spherical imagery because it maps easily onto the longitude and latitude lines of a three-dimensional sphere, and is therefore straightforward to program and process using available computer graphics techniques.
Once the image environment surrounding a particular viewpoint has been stored as an equirectangular image, it's possible to generate perspective views of the environment from a variety of viewing directions using a computer. Viewing spherical imagery using the equirectangular image format can work well for individual images, but is decidedly less convenient for viewing spherical movies.
Though spherical movies might be viewed using periodic display of equirectangular images mapped to a three-dimensional viewing sphere, this technique is rather inefficient, since the system processes much more image data than is typically displayed to the user. In part, this is due to the inefficiencies of the equirectangular image format itself, since the application of this format to the surface of a sphere results in pixel lines that shrink in length as they proceed towards the sphere's top and bottom apexes, scaled according to their length along the spherical surface. This results in storing approximately 36% more image data than will ever be seen when mapped onto a spherical surface.
Longitude/latitude based three-dimensional sphere representations commonly used for viewing spherical imagery provide similar inefficiencies as the top and bottom apexes are approached. For example, when computer graphics representations of three-dimensional surfaces are based on a discrete set of triangular polygons, though a sphere's surface should be substantially uniform, the polygons generated by this method are not. The polygons shrink in size and become more densely packed as they approach the sphere's top and bottom apexes. As a result, the computer used for viewing the spherical imagery must process significantly more geometric information for virtual camera views approaching the sphere's top and bottom apexes, even though the surface properties of the apex areas are no different from those near the sphere's equator.